Quantitative structure-activity relationships (QSAR) have been formulated for the activities of a series of benzodiazepines in rats. The lipophilic character of molecules was expressed by means of the chromatographic Rm values which were very well correlated with experimental or calculated log P values. The ideal lipophilic character for activity of benzodiazepines in the exploratory behavior test is not far from that of compounds acting in the central nervous system as unspecific depressant agents. The results of both the conflict and exploratory behavior studies might support the hypothesis of different sites of action for the antianxiety and sedative effects of benzodiazepines.